Input impedance of a monopole over a circular ground-plane of finite thickness

This paper describes a waveguide modal-expansion method for obtaining the input impedance of a monopole antenna fed through a circular ground plane of finite diameter and finite thickness by a coaxial line. The open-region antenna problem is initially transformed into a coaxial-circular waveguide junction cascading problem by properly introducing a large cylindrical wall to enclose the monopole and ground plane. The resulting waveguide cascading problem is then solved by the conservation of complex power technique (CCPT). Numerical results for the input impedance of a monopole over a finite circular bound plane are compared with experimental data. Very good agreement is observed.